1. Technical Field of the Invention
The present invention relates generally to a battery unit which includes an assembled battery module and is installed in vehicles such as automobiles, and more particularly to such a battery unit equipped with a swell limiter working to suppress swelling of cells.
2. Background Art
Japanese Patent First Publication No. 2011-216401 teaches how to pack an assembled battery module made up of a plurality of electric cells along with a control board to make a battery unit. This type of battery unit may experience swelling of each of the cells with use. Several techniques, thus, have been studied to suppress such swelling of the cells. For instance, a battery casing in which the cells are disposed has been proposed to have rigidity great enough to withstand the swelling of the cells.
Specifically, the battery casing is designed to be placed in direct contact with outer surfaces of the respective cells to suppress the swelling of the cells. Therefore, when they do not yet swell or have only swelled slightly, the cells will be subjected to mechanical pressure externally and adversely affected by heat or vibration.
For example, when the battery unit is mounted in a vehicle such as an automobile, mechanical vibration usually continues to be exerted on the battery unit during running of the vehicle. There is still room for improvement on the ease with which the cells are impacted by the heat or vibration.